1. Field of the Invention
The present invention relates to a method for manufacturing a small surface acoustic wave device with a surface acoustic wave element mounted on a circuit board, and more particularly to a method capable of manufacturing a plurality of surface acoustic wave devices stably with a high manufacturing yield at a time. This kind of surface acoustic wave device is used in a radio communication apparatus such as a mobile phone.
2. Description of Related Art
Among mobile radio communication apparatuses, mobile phones have been decreasing in size and weight, and incorporating an increased number of circuit elements to be available in a plurality of communication systems.
Electronic components to be used as such circuit elements are strongly urged to be small-sized ones to improve the mounting density thereof on a main board.
Especially, among circuit elements used in a mobile phone, surface acoustic wave devices as a key device are strongly urged to achieve low-loss and wide-bandwidth characteristics as well as highly attenuated cutoff characteristics outside the passband, and further to decrease in size and height so as to be surface-mounted on a main board.
In addition, surface acoustic wave devices such as surface acoustic wave resonators and surface acoustic wave filters are also widely used in various kinds of radio communication apparatuses, in-car apparatuses, and medical apparatuses that utilize microwave band, which are required to be further reduced in size with the size reduction of such apparatuses.
Therefore, mounting structure types such as face-down surface mounting and CSP (Chip Size Package) are becoming mainstream when mounting surface acoustic wave elements on a circuit board.
The process of manufacturing such surface acoustic wave devices is classified mainly into a “pre-process” in which a surface acoustic wave element is incorporated into a piezoelectric substrate and a “post-process” in which the surface acoustic wave element is mounted on a circuit board.
In a conventional process of manufacturing a surface acoustic wave device of a package mounting type, a plurality of surface acoustic wave elements are incorporated into a piezoelectric substrate in block to be subsequently separated into each component to obtain a plurality of surface acoustic wave element chips (pre-process). Then, each surface acoustic wave element chip is mounted into a package (post-process).
As a result, there are limitations to achieving reductions in size and height, and the conventional process also suffers from a problem that the increased number of man-hours in the post-process leads to a rise in tact and manufacturing cost, resulting in an impact on the product's unit price.
Hence, in order to further reduce the size of surface acoustic wave devices and to simplify the manufacturing process thereof, there has also been proposed a packaging method in which a plurality of surface acoustic wave elements are face-down flip-chip mounted, respectively, in areas to be surface acoustic wave devices on a circuit board, and then the circuit board is finally diced into each surface acoustic wave device in block (refer to Japanese Published Unexamined Patent Application No. 2003-110402, for example).
In this conventional process of manufacturing a surface-mounting type surface acoustic wave device, a plurality of surface acoustic wave elements are mounted on a circuit board to be subsequently separated into each surface acoustic wave device integrally with the circuit board in a dicing process.
In the dicing process, the circuit board is positioned on a base using butting pins, etc., and then diced by inserting a dicing blade between each surface acoustic wave element from the nonfunctioning surface side (opposite the surface of the piezoelectric substrate on which electrodes are formed) of the surface acoustic wave elements covered with sealing resin.
However, in a surface acoustic wave device thus manufactured in accordance with the conventional manufacturing method, since the circuit board on which the surface acoustic wave elements are flip-chip mounted is diced in the dicing process by inserting the dicing blade downward from the sealing resin side, an edge portion of the sealing resin covering the surface acoustic wave device may often be rounded or chipped.
If an edge portion of the sealing resin may be thus rounded or chipped, there occurs a problem that it is difficult to pick up the surface acoustic wave device due to a collet, etc. in the subsequent taping process of the surface acoustic wave device on embossed tape or the mounting process on an electronic circuit module, etc.
In addition, there is no dicing line on the sealing resin side that functions as a dicing guide for dimensionally accurate alignment while dicing the circuit board using the dicing blade from the sealing resin side of the surface acoustic wave device, resulting in poor alignment accuracy in the dicing process.